This invention relates to automated data storage libraries, and, more particularly, to libraries having a plurality of pickers for accessing data storage media stored in the library, and for accessing and delivering the media between media storage slots and read/write stations.
Automated data storage libraries are known for providing cost effective access to large quantities of stored data. Generally, data storage libraries include a large number of media storage slots in which are stored portable data storage media. The typical data storage media is a tape cartridge or an optical disk cartridge. A picker typically accesses the data storage media from the media storage slots and delivers the accessed media to a data storage drive at a read/write station for reading and/or writing data on the accessed media. The operation of the picker is under the control of a library controller which is coupled by wires to suitable electronics, such as an accessor or robot control, which operates servo motors to move the picker.
The need to store ever increasing numbers of volumes of data with the ability to access that data rapidly has led to the use of high capacity automated data storage libraries with multiple pickers.
Conventional automated data storage libraries having multiple pickers avoid collisions by assigning pickers to zones within the library. An example is U.S. Pat. No. 5,513,156. These zones are separated by a zone boundary area which prevent two pickers from interfering with each other. When a media is to be moved to an area outside of the normal zone of a picker, either the media is exchanged from a first picker to a second picker by delivering it to a storage slot accessible by both pickers, or the zone boundary is moved, or the second picker is moved out of the way or into a garage.
Thus, the read/write stations must be positioned at different locations in the library so that they can be separately accessed by each of the pickers in its zone. Further, if all of the data storage media requested by the host system is in one zone of the library, all of the media must be accessed by a single one of the pickers, while the other picker is idle. Still further, if a read/write station in one zone is inoperative, the picker for that zone has only reduced capability because it has no access to the other read/write stations in the other zone. As the result, the effectiveness of the library is reduced.
Additionally, the conventional library controller directly controls the operation of the pickers, and is coupled to the pickers by means of electrical wiring to operate the robot servo processor in each picker. Thus, the library is subject to failure of the wiring between the controller and the multiple pickers, and the pickers must be operated so that the wiring does not become tangled. A library having storage cells below a floor laying in a horizontal plane with wireless vehicles for accessing the storage cells is shown in coassigned U.S. Pat. No. 5,395,199, but employs a single central control processor to operate the vehicles and does not consider how to avoid possible interference between the vehicles.
Thus, the above libraries are vulnerable to the failure of the library controller or to the failure of one of the pickers, and the library effectiveness is reduced by the need to adjust the operation of the pickers because of the presence of the zones, and further reduced by the need to sense the situations requiring adjustment of the zones.
An object of the present invention is to increase the effectiveness of a library having multiple pickers.
Disclosed are multiple intelligent pickers with dynamic routing for an automated data storage library. Media storage slots for storing data storage media and a plurality of read/write stations are arranged so as to be accessible to the plurality of the pickers. A library controller receives move commands from an attached host to move media amongst the media storage slots and the read/write stations. The library controller identifies the start and end locations of the received move job, and places the move job in a job queue.
At a high level, a host will provide an identifier of the data that is to be moved, such as the volume serial number (VOLSER) of the data, and the controller or library manager determines from tables the data storage media containing the data and the storage slot holding that media. At a low level, a host will provide the identifier of the storage slot holding media with the desired data.
Each intelligent picker dynamically routes itself. Each picker comprises at least one gripper for accessing and delivering media at the media storage slots and the read/write stations, and a picker processor.
The picker processor receives information over a communication link from other pickers describing a movement of another picker for a current move job of the other picker. Upon completion of a move job, the picker selects a move job from the job queue. The move job is selected if it has both the start and the end locations accessible by the picker and which avoid interference with the movement of the other picker. Upon selecting the move job, the picker processor determines a movement for the selected move job which avoids interference with the movement of the other picker.
In one embodiment, upon determining the movement, the picker processor communicates information describing the determined movement to the other picker(s) over the communication link, and upon communicating the movement, operates the picker to conduct the move job according to the processor determined movement. In this embodiment, the movement information comprises a movement profile having the start and end locations of the move, any intermediate location at which the picker will change direction, and a clock time at which the move job commences.
In an alternative embodiment, the movement information comprises the present location and vector of the picker, and the end locations of the move.
For the purpose of this invention, the communication between the pickers and with the job queue may be hardwired or may be wireless.
For a fuller understanding of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.